Pseudogap behavior in the electronic specific heat of La2-xSrxCuO4

In La214, the electronic specific heat coefficient gamma (=C-el/T) is gradu ally suppressed with lowering T below a certain temperature T* (> T-c), whe re the in-plane resistivity rho and magnetic susceptibility chi also tend t o be suppressed slightly. Temperature T*, increasing with lowering x, is in qualitative agreement with the mean field T-c(T-co), estimated from the su perconducting gap amplitude 2 Delta(0) at T much less than T-c, as the onse t temperature T* of a pseudogap in Bi2212. The gradual suppression of gamma below similar to T-co implies that a pseudogap will also open up below sim ilar to T-co in La214 as in Bi2212. In underdoped samples, whose pseudogap- like behaviors in C-el(T) become marked, the anomaly of C-el around T-c is rather different from the BCS expectation.